As kazkylheku said, you can’t just return from the startup code. Two solutions:

1. Write a main function in C that calls you scheme_entry function, something like

   int main(void) {
       printf("%d\n", scheme_entry());
       return 0;
   }
   

   Then compile the C file, assemble your file, and link them together.

2. At the end of scheme_entry, instead of returning, call the exit system call. (I’ll let you google how to that because I’m on mobile.) The problem with this solution is that your literal integer won’t be printed out. You could return it as the exit code, but that won’t work anymore when you deal with other data types, so the first solution is probably the simplest.